Pareto

Pareto ChartPareto Chart

A Pareto chart is a bar graph. The lengths of the bars represent frequency or cost (time or money), and are arranged with longest bars on the left and the shortest to the right. In this way the chart visually depicts which situations are more significant.

• When analyzing data about the frequency of problems or causes in a process.

• When there are many problems or causes and you want to focus on the most significant.

• When analyzing broad causes by looking at their specific components.

• When communicating with others about your data.

When to Use a Pareto Chart

Pareto Chart ProcedurePareto Chart Procedure

• Decide what categories you will use to group items.Decide what categories you will use to group items.• Decide what measurement is appropriate. Common Decide what measurement is appropriate. Common

measurements are frequency, quantity, cost and time.measurements are frequency, quantity, cost and time.• Decide what period of time the Pareto chart will cover: Decide what period of time the Pareto chart will cover:

One work cycle? One full day? A week? One work cycle? One full day? A week? • Collect the data, recording the category each time. (Or Collect the data, recording the category each time. (Or

assemble data that already exist.)assemble data that already exist.)• Subtotal the measurements for each categorySubtotal the measurements for each category


• Determine the appropriate scale for the measurements Determine the appropriate scale for the measurements you have collected. The maximum value will be the you have collected. The maximum value will be the largest subtotal from step 5. (If you will do optional steps largest subtotal from step 5. (If you will do optional steps 8 and 9 below, the maximum value will be the sum of all 8 and 9 below, the maximum value will be the sum of all subtotals from step 5.) Mark the scale on the left side of subtotals from step 5.) Mark the scale on the left side of the chart.the chart.

• Construct and label bars for each category. Place the Construct and label bars for each category. Place the tallest at the far left, then the next tallest to its right and tallest at the far left, then the next tallest to its right and so on. If there are many categories with small so on. If there are many categories with small measurements, they can be grouped as “other.”measurements, they can be grouped as “other.”

• Steps 8 and 9 are optional but are useful for analysis and Steps 8 and 9 are optional but are useful for analysis and communicationcommunication


Example: High Inventory Shrinkage at local Drug Store

• This fishbone diagram was drawn by a manufacturing team to try to understand the source of periodic iron contamination. The team used the six generic headings to prompt ideas. Layers of branches show thorough thinking about the causes of the problem.

• Fishbone Diagram Example

• For example, under the heading “Machines,” the idea “materials of construction” shows four kinds of equipment and then several specific machine numbers.

• Note that some ideas appear in two different places. “Calibration” shows up under “Methods” as a factor in the analytical procedure, and also under “Measurement” as a cause of lab error. “Iron tools” can be considered a “Methods” problem when taking samples or a “Manpower” problem with maintenance personnel.

Create a Fishbone Create a Fishbone DiagramDiagram

Analyze process dispersion with this simple, visual tool. The resulting diagram illustrates the main causes and subcauses leading to an effect (symptom). Start using Fish Bone Tool.

Engineering

Pareto